214 "GIANTS' BONES*' IN PATAGONIA CHAP. the formula is the same as in Typotherium. The animal seems to have had nails rather than hoofs. The thumb was opposable. The fibula is fused below with the tibia, whereas in the last genus these two bones are quite separate from each other. SITE-ORDER 5. TOXODONTIA The group Toxodontia,1 like so many others, is exceedingly hard to define. úTor are its - limits any easier to mark out than many others of the groups of Ungulates. It will be best perhaps to give an account of Toxodon, and of a few types which seem to lie near it in the system, and then to indicate how far they resemble or depart in structure from other Ungulates. Too&odon itself is known from complete skeletons. It lived in Argentina during the " Pampean " period, which seems to be of the Pleistocene age. A large number of species, however, have been described, some of which seem to go farther back in time, and to have existed during the Miocene period further south in Patagonia. The size of this creature was about that of a large Rhinoceros; it has a bulky body and a large head, which was borne low down, on account of the bending downwards of the anterior vertebrae; in this aspect the figures of the skeletons recall Gttyptodon and similar Edentates. The beast was discovered by Darwin, and originally described by Owen. ** During his (Mr. Darwin's) sojourn in Banda Oriental," writes the Rev. H. Hutchinson, " having heard of some c giants* bones * at a farm- house on the Sarandis, a small stream entering the Rio USTegro, he rode there, and purchased for the sum of eighteenpence the skull which has been described by Sir R. Owen. The people at the farm-house told Mr. Darwin that the remains were exposed by a flood having washed down part of a bank of earth. When found, the head was quite perfect, but the boys knocked the teeth out with stones, and then set up the head as a mark to throw at." The whole of the Pampean area is a valley of dry bones, and the remains of Toxodon are abundant there. The skull of To&odon is not unlike that of a horse in general aspect; but the orbit is not separated from the temporal fossa. The premaxillae aiJe famished above with a slight protuberance directed towards 1 Cope, American Naturalist, xxxt 1897, p. 485.